Since the introduction of automatic transmissions, hydrodynamic converters have been the connecting element between a prime mover and the transmission proper. A converter makes possible, on one hand, a comfortable jolt-free start through the slip and at the same time dampens irregularities of rotation of the internal combustion engine. On the other hand, the fundamental increase of the torque makes available a great starting torque.
According to the prior art, a hydrodynamic converter is comprised of an impeller, a turbine wheel, the reaction element (guide wheel, stator) and the oil needed for torque transmission.
The impeller, which is driven by the engine, moves the oil in the converter to a circular current. Said oil current hits upon the turbine wheels where it is turned around in flow direction.
In the hub area, the oil leaves the turbine and arrives at the reaction element (guide wheel) where it is again turned around and thus fed to the impeller in the proper flow direction.
Due to the reversal, in the stator a torque generates whose reaction increases the turbine torque. The ratio of turbine torque to pump torque is designated as torque increase. The greater the rotational speed difference between pump and turbine, the greater the torque increase which has the maximum magnitude when the turbine is stationary. As the turbine rotational speed increases, the height of the torque consequently decreases. If the turbine rotational speed rises to about 85% of the pump rotational speed, the torque increase=1, that is, the turbine torque is equal to the pump torque.
The stator, which props itself toward the transmission housing via the freewheel and the stator shaft, flows freely in this state in the current and the freewheel is rolled over.
From this point on, the converter works as pure flow clutch. During the conversion, the stator remains still and is propped toward the housing via the freewheel.
Converters are known from the prior art which comprise one converter lock-up clutch and one primary clutch, said primary clutch being inserted between engine and converter and the lock-up clutch between engine and transmission.
Such converters are usually provided for vehicles which perform works at very low speeds but can also move at high speeds. Within the scope of DE 195 21 458 Al is described, by way of example, a converter with lock-up clutch and primary clutch. According to the prior art, there are, respectively, provided for converter lock-up clutch and primary clutch its own pressure supply and its own valve unit.
Converters are also known which comprise one converter lock-up clutch and are especially used in transportation vehicles such as dumpers or cranes. On the other hand, converters with primary clutch are used in working machines like wheel loaders or lift trucks.
The problem on which this invention is based is to provide a hydrodynamic converter in which the pump is detachably connectable via a primary clutch with the output from the engine.